Embedded development: tips and techniques -- seven techniques to meet the real-time deadline

　　 The embedded system must meet the real-time deadline , In order to effectively operate as expected . No one likes to press a button , wait for 30 second , The system finally responds . what's more , Safety critical systems need to be completed on time , Otherwise, something very bad may happen , Such as injury or death . There are many ways to ensure that the embedded system can be completed on time , But here are seven tips to help embedded developers ensure that they meet their deadlines as expected .

　　 skill 1—— strive for 30% In my spare time

　　 Everyone wants to get the maximum value from each component selected for the product . In less than 100% The speed of running the microcontroller , It feels like the product is over designed . However , The fact is that , To meet real-time requirements and deadlines , Developers should really set their systems to CPU Free time in 30% about . Why is it so high ? Executive theory RAM( Monotonic rate analysis ) The developers in this field will find that , Meet real time requirements 、 The theory of running the scheduler and handling interrupts is the largest CPU The load is 69.3%. Putting more pressure on the processor means , In the worst case , The possibility of not meeting the requirements of real-time system is greatly increased .

　　 skill 2—— Use tracking tools for accurate measurements

　　 A few years ago , Developers will map out what theoretically happens in their system , Implement it , Then pray that what happens in the microcontroller is what they think is happening . From then on ,SWD、ETM And other tracking protocols and other new tools have emerged , Allows developers to monitor the instructions being executed in the microcontroller , The impact on real-time performance is minimal . Developers often assume how their system will execute code , But use tracking tools , Not only can we test hypotheses , It can also provide developers with minimal 、 Maximum and average execution time , Enable them to adjust and validate their real-time models . Use these tools to improve and understand assumptions , And realize what the system is doing .

　　 skill 3—— Careful choice RTOS Priorities

　　 Many embedded developers don't know how to choose RTOS priority . When forced to choose a priority , They simply make a quick psychological comparison with other tasks in the system , Then choose the one they think should be . Engineering is rarely involved in decision-making , More speculation . Only after carefully analyzing the interaction between tasks , And make sure that all tasks can be completed before the deadline in all cases , To choose RTOS priority .

　　 skill 4—— Conduct RMA analysis

　　 Monotonic rate analysis (RMA) It's a technology , Developers can use it to analyze their recurring tasks , And make sure to set the priority , To meet all deadlines . For developers ,RMA It's a good starting point , It can be used to ensure that the integrity of their system is built on a solid foundation .

　　

 

　　 skill 5—— Choose the right microcontroller for the job

　　 Choosing a microcontroller with too little horsepower for the job at hand can lead to a nightmare solution , That is, constantly optimize 、 Cutting and fighting with source code . Choosing the right microcontroller is a challenge . A good rule of thumb is to start with the high-end devices of the microcontroller family of interest , Prototype the system , And start to understand the code 、 Its execution mode and the overall performance of the system . If the power of the microcontroller is too large , Just switch to a microcontroller with a low success rate . But don't forget , in many instances , Products tend to add more and more functions over time , Therefore, embedded developers can keep the system working normally by choosing a microcontroller that exceeds their needs , Even if functional creep is at work .

　　 skill 6—— Create software architecture

　　 Pre designed system , Model and create software architecture . An architecture will help developers understand major software components , What are their inputs and outputs , And how they interact . Understanding these main parts can identify areas that are not well understood , This can guide engineers to better study and understand these areas before writing product code . A well structured code base will produce understandable code , And meet its deadline .

　　 skill 7—— Keep testing

　　 Software changes . Functions are added 、 enhance , Sometimes even deleted . Changes to the code base will inevitably affect the performance of the real-time system , And may lead to the priority change required to keep the system running as expected . The only way to ensure the continuous operation of the system is continuous testing 、 Measure and evaluate the operation of the system . Integrate testing and measurement into the embedded software development process .

　　 Conclusion

　　 Management time and meeting deadlines are the most important factors to consider when developing real-time embedded systems . Following these tips can begin to help embedded developers understand how their systems work , And make sure they will meet all the system deadlines they are given .